Nowadays, in the commercial field, for the POS device, password keyboard, ATM device and other electronic devices, the keyboard is the part for inputting data information. The input or stored high sensitive data information such as the bank information, password, and register code and so on, are usually attacked and stolen in the situation of unauthorized permission. Therefore, the protection for the data is paid more and more attention, various forms of keyboard protection devices and methods continue to emerge.
The general keyboard protection is mainly focused on the whole protection of the devices, especially on the protection of preventing the disassembly of the housing. A tamper-evident contact are usually disposed on the keyboard print circuit board (PCB), a conductive adhesive is pressed on the tamper-evident contact through the housing of the device to turn on the tamper-evident detection circuit. If the attacker tries to disassemble the housing to attack the inner of the keyboard, the conductive adhesive will not contact the tamper-evident contact and the tamper-evident detection circuit is short circuit thereby triggering the corresponding security measure to delete the high sensitive data information stored in the inner of the device. This protection method is not precise enough, the attacker may not contact the tamper-evident contact and attack the key gold finger region of the keyboard PCB to obtain the high sensitive data information through holing, piercing the housing and other attacking method. There is another protection method using a keyboard protection board to protect the key region of the keyboard, such as description of the CN patent ZL201020297100.2, the keyboard protection device comprises a key for the keyboard, a silica gel and a keyboard PCB. A keyboard protection board is covered and adhered on the gold finger of the keyboard PCB and is electrically connected and turned on through contact on the keyboard protect board. The keyboard protection board is with a flexible film as the base and protects the gold finger on the keyboard PCB through printing a conductive MESH protection circuit, and protects the periphery of the gold finger through a tamper-evident layer of the keyboard protection board. The keyboard protection board focus on the protection of the front and the periphery of the gold finger, when the attacker holes or uncovers the keyboard protection board, the corresponding security mechanism is triggered to delete the high sensitive data information stored in the inner of the electronic device. However, to the conduction of the conductive MESH protection circuit for the front protection, a gap or insulation matter is disposed between two lines printed on the conductive MESH protection circuit. This allows an attacker to find loopholes to attack, steal the high sensitive data stored information stored in gold finger. Further, the MESH protection circuit is printed directly on the flexible film, pressure on the keyboard key applies directly on the flexible film and the MESH protection circuit, frequent or improper operation easily cause the protection circuit traces rupturing, thereby reducing the lifetime of the keyboard protection board.